Species invasions are occurring worldwide at an unprecedented rate, with extreme ecological and economic impacts (Mooney and Cleland 2001, Sala et al. 2000, Vitousek et al. 1997). While the Global Invasive Species Database lists over 660 species of ecological and economic concern, less than 12% of invaders occur in marine ecosystems. Despite the rarity of these events, one such invasion is currently unfolding in the Western Atlantic and Caribbean Sea, and is progressing at a rate and magnitude never before documented in any marine system.